1. Field of the Invention
The present invention relates to a method for measuring the amount of positional deviation which measures the amount of positional deviation between recording positions of a plurality of head modules of a recording head, and an image-recording device which measures the amount of positional deviation using the method.
2. Description of the Related Art
As a recording system of an ink jet printer (image-recording device), a line system which records an image with a single drawing pass by a line head along with transport of a recording medium is known. In the line system, a long line head (recording head) is used along a width direction (main scanning direction) of the recording medium orthogonal to a transport direction (sub scanning direction) of the recording medium. It is not realistic to integrally form the line head of silicon wafer, glass, or the like due to problems of yield, heat, cost, and the like. For this reason, in the line system, a line head in which head modules each having nozzles arranged in a two-dimensional manner are arranged in parallel in the width direction of the recording medium is usually used.
When performing image recording using the line head, if the position of the individual head module is deviated in the sub scanning direction, the recording position of the individual head module undergoes a positional deviation in the sub scanning direction; thus, there is a problem in that quality of a recorded image is degraded. For this reason, various methods which detect the amount of positional deviation in the sub scanning direction of the recording position of each head module are suggested.
In a method for measuring the amount of positional deviation described in JP 4770256B, first, line patterns extended long in the width direction of the recording medium are recorded at intervals of n pixels in the sub scanning direction centering on a reference line by one of adjacent head module to form a first line group. Simultaneously, line patterns are recorded at intervals of n+1 pixels in the sub scanning direction centering on the reference line by the other head module to form a second line group. Next, the first line group is compared to the second line group to identify a first line pattern of the first line group and a second line pattern of the second line group aligned in the transport direction. The amount of positional deviation is calculated as [k×((n+1)−n)] pixels based on the amount of positional deviation (a k-th position from the reference pattern) from the first and second line patterns. With this, it is possible to measure the amount of positional deviation in the sub scanning direction between the recording positions of adjacent head modules in terms of pixels.